(Ecstasy) is a popular drug of abuse especially among youth in the population. Use of MDMA is associated with acute physiological effects (e.g. hyperthermia) which may lead to serious organ damage. MDMA is neurotoxic and cognitive and psychological deficits have been noted in consumers of the drug. Furthermore, some individuals meet the criteria for dependence on MDMA. There is currently an unmet medical need for a therapeutic agent to combat MDMA overdose and abuse. Blockade of serotonin 5-HT2A and 11A adrenergic receptors have been shown to antagonize a range of MDMA- induced behavioral and physiological effects in animal models. The goal of this project is to elucidate structural features of our lead molecule nantenine that are required for antagonism of 5-HT2A and 11A adrenergic receptors. We will test the central hypothesis that structural modifications of nantenine will yield novel 5-HT2A antagonists and novel 11A adrenoceptor antagonists. To test this hypothesis we will engage a structure-activity relationship (SAR) study involving three specific aims. In the first specific aim, we will examine the effects of replacement of substituents on ring A of nantenine on antagonizing the targeted receptors. For the second specific aim, the pharmacophoric relevance of the methylenedioxyphenyl ring of nantenine will be evaluated through the synthesis of novel heterocyclic derivatives. In specific aim 3, the importance of the N-substituent group will be analyzed. Selected compounds will be advanced to behavioral assays in rodents in order to characterize their pharmacological profiles as potential MDMA antagonists.